a) Field of the Invention
This invention relates to biodegradable and biocompatible agricultural mulch and a method of preparing same. More particularly, the present invention is directed to an agricultural mulch having a programmed duration of biodegradation.
b) Description of Prior Art
Ever since the start of the present century, numerous attempts have been made to produce an agricultural mulch derived from various fibre mats. From this, it was found that no paper or cardboard would resist for a long time to degradation. This is why all the efforts have been concentrated on the necessity of finding an efficient protection against biodegradation.
On the other hand, it is well known that polylactide (PLA--polymer derived from 2-hydroxy-propanoic acid) is one of the rare polymers which are considered to be truly biodegradable. Its degradation cycle is based on a process of hydrolysis of the polymer chain. It is decomposed into lactose, water and carbon dioxide. PLA is also completely biocompatible. This means that neither the polymer nor its degradation products, are damaging to the health of living organisms. For this reason, the medical use of PLA (surgery) is well known.
Recent technological developments in the production of PLA, have made it possible to provide large quantities of PLA at competitive prices. Moreover, during its production, it is possible to modify the polymer chain so as to control its resistance against degradation. However, PLA is a material with poor mechanical properties. Since PLA is too crumbly and too brittle, it cannot be used as a film of PLA which can be mounted by means of a standard mechanical unrolling device. PLA therefore needs a support, however, the latter must at least preserve all the desired properties of PLA.
There is therefore a need for a suitable PLA-support combination which provides a good heat insulation, so that during the night it preserves humidity of the ground, and during the day, it permits a progressive but not excessive warming of the ground as it often happens in the case of a mulch of plastic material.
It is therefore an object of the present invention to provide a mulch which enables the temperature of the ground to constantly remain within an optimum growth zone, which significantly advantages the plants at the start of the season.
It is another object of the present invention to provide a mulch which offers excellent thermal insulation to young seeds at the start of the season, while completely preventing the growth of weeds, which cannot grow through the mulch.
It is another object of the present invention to provide a mulch which makes it possible to dispense with the use of dangerous products by fumigation, such as methyl isothiocyanate, chlorinated hydrocarbons, and the like.
It is still another object of the present invention to provide a mulch which will remain in place until complete biodegradation.
It is still another object of the present invention to provide a method of preparing a mulch which overcomes all the disadvantages of those described in the prior art.